The present invention relates to a means for providing fuel composition information to a vehicle engine control computer to facilitate the use of alternate fuel mixtures in internal combustion engines, and to a means for reminding the person refueling the vehicle to provide the requisite fuel composition information to the engine control computer before adding fuel to the vehicle.
It is well known that ever tighter emissions regulations and petroleum depletion have prompted research into the feasibility of using alternative fuels in internal combustion engines. Currently, ethanol/gasoline and methanol/gasoline mixtures are among the alternative fuel possibilities being considered.
Alternative fuel mixtures exhibit physical properties and performance characteristics which are different from pure gasoline, including dissimilar combustion burn rates, volumetric energy content, vapor pressures, octane ratings, and heats of vaporization. The operating parameters of internal combustion engines utilizing alternative fuels must be adjusted to accommodate such differences in order for such engines to operate efficiently. The operating parameters which must be adjusted include the air bypass, fuel flow, spark timing, and air/fuel ratio.
The aforementioned adjustments can be made automatically by an engine control computer. Engine control computers are well known and are commonly used in vehicles. See, for example, U.S. Pat. No. 4,706,630 to Wineland et al. However, in order for an engine control computer to make accurate adjustments, certain information concerning the composition of the fuel being burned in the engine, such as alcohol fraction, should be known by the computer. To the extent that erroneous fuel composition information is sent to the computer, adjustments made to the engine will be improper. Improper engine adjustments, in turn, result in poor engine performance and excessive emissions. Thus, accurate fuel composition information is important to the viability of alternative fuel use in internal combustion engines.
The current method of providing fuel composition information to engine control computers is through the use of in-line fuel sensors which exploit differences in physical properties between gasoline and ethanol or methanol to measure the instantaneous composition of fuel flowing past the sensor. The sensor then sends a signal to the computer which corresponds to the composition of the fuel flowing past the sensor. An example of this method is found in U.S. Pat. No. 4,594,968 issued to Degobert et al. wherein the composition determination of an alcohol-gasoline mixture is based on the degree to which light is absorbed by the mixture. This information is then sent to an engine control means.
Another example is found in U.S. Pat. No. 4,909,225 to Gonze et al. which discloses the use of a sensor such as a capacitive dielectric sensor to determine the composition of a fuel mixture. This information is used to control the operating parameters of an internal combustion engine.
Though potentially very useful, currently available fuel sensors are inherently inaccurate and unreliable. The distance between the sensor and the intake manifold of the engine means that the composition of the fuel being instantaneously sensed by the sensor is different from the fuel actually flowing into the engine. The engine control computer will thus adjust the engine to accommodate the fuel being instantaneously sensed, but the composition of this fuel can often be different from the fuel actually being combusted in the engine. In addition, when multicomponent fuel is agitated, an emulsion forms under certain conditions which degrades fuel sensor accuracy, thereby resulting in an erroneous signal being sent to the engine control computer.
Additional inaccuracies exhibited by currently available fuel sensors stem from the environment in which they operate. Foreign materials accumulate on the sensing surfaces over time and continually degrade the fidelity of the signal sent to the computer. Temperature variations in the fuel and mechanical stress on the sensor also tend to adversely affect the signal.
Accordingly, it is seen that the need exists in the art for more accurate and reliable means for informing engine control computers of the composition of fuel being introduced into the internal combustion engine of a vehicle. Such a need, if fulfilled, would facilitate the use of alternative fuels in vehicles by allowing internal combustion engines to efficiently operate on such fuels, resulting in improved engine performance and decreased pollution.